Meeting Abstract
Changes in temperature alter muscle kinetics and these effects can be observed during whole-organism performance. Some organisms use elastic recoil, which is far less sensitive to temperature, to power thermally robust movements. However, some systems (e.g. frog jumping) remain sensitive to temperature despite well-documented utilization of elastic mechanisms. For jumping frogs, the latch controlling the storage and release of elastic energy arises, in part, through dynamic changes in mechanical advantage (MA). Here we use an in-silico/in-vitro muscle preparation to understand how changes in temperature affect the flow of energy from muscles to tendons, and ultimately to the body, in a system using an MA latch. We use an in-vitro preparation of the plantaris longus muscle-tendon unit (MTU) that interacts with an in-silico model of a limb with changing MA and a mass being accelerated through a real-time feedback controller. We quantify the amount of energy stored in and recovered from elastic structures and the additional contribution of direct muscle work after unlatching. As expected, colder MTUs take longer to develop force and overcome the MA latch. Additionally, warmer MTUs continue to develop force far beyond what is needed to overcome MA before the mass has reached an appreciable velocity, storing more energy in elastic structures. We also find that the contribution of direct muscle work after unlatching is substantial and increases significantly with temperature. Our results suggest that the degree of thermal robustness achieved by a spring actuated system depends strongly on the nature of the latch that mediates energy flow and the inertia of the mass being accelerated.
